The present invention relates to an electrolyte containing a solvent and an electrolyte salt and a secondary battery using the same.
In recent years, portable electronic devices such as combination cameras, digital still cameras, mobile phones, and notebook personal computers have been widely used, and it is strongly demanded to reduce their size and weight and to achieve their long life. Accordingly, as a power source for the portable electronic devices, a battery, in particular a small and light-weight secondary batter capable of providing a high energy density has been developed.
Specially, a lithium ion secondary battery using insertion and extraction of lithium ions for charge and discharge reaction, a lithium metal secondary battery using precipitation and dissolution of lithium metal and the like are extremely prospective, since such secondary batteries are able to provide a higher energy density compared to a lead battery and a nickel cadmium battery.
As an electrolyte of the lithium ion secondary battery and the lithium metal secondary battery, combination of an ester carbonate solvent such as ethylene carbonate and diethyl carbonate and an electrolyte salt such as lithium hexafluorophosphate is widely used, since such a combination has high electric conductivity and stable potential.
In addition, regarding electrolytic solution composition, various techniques have been proposed for the purpose of improving battery characteristics such as cycle characteristics and storage characteristics. Specifically, in order to improve cycle characteristics and storage characteristics, a disulfonic acid anhydride (refer to Patent documents 1 to 3), a nitrile compound (refer to Patent document 4), a diisocyanate compound (refer to Patent document 5) and the like are used. Further, in order to improve swollenness characteristics, a fluorinated ether compound and the like are used (refer to Patent document 6). In addition, a dicarboxylic anhydride such as a succinic anhydride (refer to Patent document 7), sultone, a pyrrolidone compound (refer to Patent documents 1 and 2) and the like are used.